[Catalyst] How to get from

[will trillich]

Short version: we're wondering how a method from inside the SCHEMA can
return other
objects besides the one that got passed in. That is, we have $obj
(with its own ID
number) but we want to FIND a different object -- same type, but with
a different
ID number. What's the mechanism for that, inside the schema package?

Long version:

We've got a schema defined for hierarchical groups:

MyApp::Schema::DB::Result::Group
__PACKAGE__->add_columns(
  "id",
  { data_type => "INT", default_value => undef, is_nullable => 0, size => 11 },
  "name",
  {
    data_type => "VARCHAR",
    default_value => undef,
    is_nullable => 0,
    size => 90,
  },
  "parent",
  { data_type => "INT", default_value => undef, is_nullable => 1, size => 11 },
);
__PACKAGE__->set_primary_key("id");
__PACKAGE__->belongs_to( parent => 'MyApp::Schema::DB::Result::Group'
=> 'parent' );
__PACKAGE__->has_many( subgroups => 'MyApp::Schema::DB::Result::Group',
    { 'foreign.parent' => 'self.id' },
    { order_by => 'name' },
    );

So when there's an ID number in "parent" the current group object has
a parent group
object. When there's no ID (or it's zero) then that's the top-level group in its
hierarchy.

Creating a method for the top-level group is simple:

sub top {
  my $self = shift;
  my $top = $self;
  while ( $self = $self->parent ) {
    $top = $self;
  }
  return $top;
}

If we're looking for a certain PARENT with a given ID, that's simple too:

sub specific_parent {
  my $self = shift;
  my $id   = shift;
  while( $self->id != $id ) {
    return unless $self = $self->parent;
  }
  return $self;
}

But how do we go about creating a method to look for a specific group by ID
that may not be in the parent-chain?

sub specific_group {
  my $self = shift;
  my $id   = shift;
  return unless $self->some_manner_of_valid_id_check( $id );
  return $self->BLACK_MAGIC_HERE->find( {id=>$id} );
}

So the real question is, how do we get from $self to ->find() ?